Search the Community

12_27_2021: Puritan Rd to Egg Rk to Nahant E Point to Dread to Off Rk. 10:45am – 2:45pm. Bob L alone in green Explorer. LT 11:09am 1.1ft, HT 5:20pm 8.9ft. Tidal range 7.8ft, neaps, half-moon. 35F. 5kts NW wind. 1-2 foot moderate period swell. The goals today were to check out local slots and rock faces, and to get in a little winter distance paddling. The ground track is shown in Figure 1. The calm conditions and low water provided an opportunity to assess the water levels for which various slots and passages are active. Because of the low water, the gardening in Nahant was mostly riding rock faces, ledges, and a few short slots defined by isolated rocks at headland edges. The launch was around 10:45am from Puritan Road, Swampscott. The crossing of Nahant Bay was a little chilly in >5kts WNW wind and temps <35F. The stingy sun was behind high thin clouds. I arrived to Egg Rock at about low tide (LT). The waves were 1-2 foot and moderate period. These provided an excellent opportunity to ride rock faces in the gut and down the south side of the island. The gentle conditions were perfect for timed capture of swell energy around headlands. I also ran a small northern low-water slot, which is not remotely possible with more severe waves. The slot location is shown in Figure 2. Assuming the run was at LT, the water level was at today’s LT baseline of 1.1ft above the Mean Lower Low Water (MLLW) chart datum. Next was the Spouting Horn on Saunders Ledge in Figure 3. Despite the mild conditions, breaking waves here were sufficient to push a kayak onto the Horn ledge. The outer wide passage, shown in Figure 3 between the Horn and the back ledge, was entirely out of the water. Figure 3 also shows the deep Saunders Ledge slot that was also dry. However, it was barely possible to run the Back Passage, a small “creek” separating Saunders from the mainland. I was there about 30 minutes after LT, with a tidal range of 7.8ft. By the Rule of Twelfths*, this suggests a rise of 7.8/12ft = .65ft in the first hour after LT on a baseline of 1.1ft over MLLW. Consequently, the estimate is that the Saunders Back Passage can be run at 1.1+.65x0.5 = 1.4ft above MLLW. By referencing “passage depths” to MLLW it is possible to determine availability of a slot from the data in the Tidelog for any day and time of the year. This is useful information. For example, there have been situations where it was unwise to approach the Spouting Horn in rounding Saunders Ledge so having the Back Passage was desirable. The insert in Figure 3 is from the chart showing a (2) over the back of Saunders Ledge. This is the drying height of the back ledge referenced to the MLLW chart datum for soundings. A tiny passage through the back ledge is likely not as high as an overall drying height on a large ledge, hence drying height is a more conservative estimate when available. That is why it is useful to assess slots and passages from the kayak, preferably in very calm conditions, to develop an understanding of passability. Finally, all these numbers and rules of thumb are approximate so we only ever get a rough estimate. Figure 4 is a summary of chart datum definitions. Sometimes drying heights are referenced to LAT (Lowest Astronomical Tide) and land heights to Mean High Water (MHW). Figure 1: Ground track for 12_27_2021 paddle. Figure 2: Egg Rock low-water northern slot circled. (LAT 42o26.055’, LON -70o53.808’, low tide, 1.1ft above MLLW). Figure 3: Saunders Ledge Passage, Slot, Back Passage (LAT 42o25.467’, LON -70o54.453’, 1.4ft over MLLW), and Spouting Horn. Figure 4: NOAA referenced depths. Chart depths based on Mean Lower Low Water (MLLW), land heights on MHW (Mean High Water) and drying heights on MLLW. Sometimes drying heights are based on Lowest Astronomical Tide (LAT). Also note that the liberal state of MA has private ownership to the MLLW, whereas most states, including TX, have ownership to high water. At this point, around 11:50am, I entered the East Point pocket cove for a quick lunch. It was an opportunity to study some of the seams in the diabase gabbro. By examining some of the cleaved seams, I thought I saw ceramic rock coverings similar to the primordial volcanic layers on Lubec’s Quoddy Head. Chilly overcast skies and fear of hypothermia dictated no further geological exploration today – to be continued on a later trip! Hopping back in the boat, I headed to East Point. The Matador slot was completely dry. It probably required another 3-4 feet of water before passage. I was there an hour after LT so, by the Rule of Twelfths, there was 1/12*tide range of depth over today’s baseline of 1.1ft. That means 1.1+1/12x7.8 = 1.75ft over MLLW. Therefore, we need at least 1.75+3.0 = 4.75 feet over MLLW to run the Matador. Despite the lack of a passage, the Matador headland provided a wonderful ride into the south rock face. This would not be possible in normal conditions. I paddled to the back of the Matador – an area we called the Ricardo Waterfall during the November 18th coasteering session. It was a ledge today instead of a connection to a waterfilled Matador basin. Nevertheless, a small “Ricardo Waterfall” was still active on the ledge. The Matador is shown in Figure 5. Due to the ability to ride very close to the rock edge, the runs along the south rock faces of East Point were excellent. There were also a couple of headland rocks with slots that allowed timed passage with low probability for catastrophe. I carefully examined the Subterranean and QUAD passages. The Subterranean looked promising from the east end, but had rock blockage on the west end. I went to the back of the east end and noted the upraised “bench” which was probably three feet above the water. Last summer, in a high-water attempt at running the passage, I had been swept over that bench by a swell. As intimidating as the bench was, an adjacent narrow passage was possible today. The west end is often the entrance to the Subterranean, and either-way would have to be passable. I estimated that another foot of water would allow the boat to get through. From the hour one analysis above, that implies >2.75 feet over MLLW is necessary to have a passable west end on the Subterranean. Although it contained some water, another foot was also necessary to clear an overhung area in the QUAD #2 Slot. The QUAD #1 Slot had a large rock on the base of the slot. Waves were riding up to it today, but there was nowhere near sufficient water to carry a boat over. It looked like two more feet were needed for a total of >3.75 feet over MLLW. The QUAD and Subterranean slots are indicated in Figure 6. While the big three; Matador, Subterranean, and QUAD were dry, I did find an excellent low-water, low-conditions slot on the Shag Rocks. It is shown in Figure 7. I’ve known about this slot for a while, but rarely try it. Conditions on the Shag Rocks often make it impossible to run complicated slot paths because there is no safe zone. Today, I was able to run the Shag T-slot in both directions shown in the figure before returning to the southern rock faces on East Point. After rounding the Matador headland on a swell, I paddled back across to Egg Rock. Because of higher water, the low-water north passage in Figure 2 was more vulnerable so it was necessary to time the swell in order to cross it. Figure 5: Matador Slot (LAT 42o25.202’, LON -70o54.148’, >4.75ft over MLLW), Headland, and Ricardo Waterfall. Figure 6: Subterranean Passage (LAT 42o25.067’, LON -70o54.235’, >2.75ft over MLLW) entrance and exit, and QUAD Slots #1 (LAT 42o25.037’, LON -70o54.252’, >3.75ft over MLLW) and #2 (>2.75ft over MLLW). Figure 7: Shag Rocks low-water T-passage. (LAT 42o24.880’, LON -70o54.383’). I then padded north to Dread Ledge on the Swampscott side of Nahant Bay. It was about 2:00pm so my exploration of Dread and Galloupes would be at the second hour after low tide. The NW wind had dropped and the sun briefly appeared. The sky to the east was clearing. Dread Ledge is a spectacular rock garden. The major features are shown in Figure 8a, including the Daymarker Ledge, Inner and Outer Guts, and the largest island of the Ledge. The Dread Ledge Daymarker Passage is almost always unpassable due to conditions, but today I was able to gingerly cross from a south entrance that had about a half foot of water. From the Rule of Twelfths, two hours after low tide has (1+2)/12 = ¼ the tide range of water over the baseline. Consequently, we have 1.1+1/4*7.8 = 3.05 feet of water over MLLW as an estimate of the Dread Daymarker passability depth. Figure 8b shows the Daymarker Passage. Continuing onto Dread Ledge itself, the back and front passages in Figure 8c were already under water and passable. It was a happy circumstance that the two Inner Gut Tables were barely awash at almost exactly two hours after LT, indicating a table height of 3.0 feet over MLLW. In big conditions these Tables in Figure 8c create enormous turbulence covering the entire Inner Gut. During a recent storm, I spent 45 minutes trying to figure out how to cross the basin because of the conditions introduced to the Inner Gut from the Tables. An estimate of water depth and wave height on the Tables provides an indication the penetrability of breaking waves into the Inner Gut basin as well as whether the breaks are dumping or surging. Figure 8a: Dread Ledge. Figure 8b: Dread Ledge Daymarker Passage. (LAT 42o27.379’, LON -70o53.687’, 3.05ft over MLLW). Figure 8c: Dread Ledge Back (LAT 42o27.484’, LON -70o53.701’) and Outer Passages (LAT 42o27.491’, LON -70o53.667’), and the Tables. (Outer, LAT 42o27.552’, LON -70o53.662’, Inner, LAT 42o27.585’, LON -70o53.656’, both awash 3.0ft over MLLW). The Rule of Twelfths suggests that in the next hour there would be a depth increase of 3/12 to 6/12 times the tide range, or 1.95ft to 3.9ft of water. During this time, I visited my favorite Galloupes Point and Off Rock passages, while running rock faces, ledges, and headland rock slots in the calm conditions. It is important to emphasize that low amplitude moderate swell provides a unique opportunity to capture wave energy in rock gardens - with a high probability of returning with an undamaged boat! Figure 9 shows one of my favorite recent discoveries that I call the Pool Slot – due to the presence of a pool at the overhead mansion. If you can get into the south entrance, the slot provides a strong push to the north exit. On exiting the “water slide” it is better to have the boat on a severe edge and allow the water to turn it outward. Looking at probably >3 feet of elevation around a dry crevasse, I was reminded today that this slot is passable only at high water. Moving east, the next Galloupes slots in Figure 10 sit under another structure that looks like a pavilion. This one has an array of tall windows visible from Nahant, so provides a public service to weary kayakers looking for landmarks without bothering with the compass and chart. Both the Outer and Inner Pavilion Slots were passable when I arrived. These slots can be very tricky in conditions. Water bunches up on the east side of the Inner Slot to present a broad “waterfall” into the basin. The Outer Slot concentrates swell energy and can be surprisingly powerful even in low amplitude swell. I was probably here halfway into the third hour so had 4 feet of water over MLLW. The Outer Slot was deep, and the Inner Slot had probably a foot of water so just barely passable. The next slots to the east of the Pavilion Slots are called the mini-Subterranean shown in Figure 11. They sit under a large complex under construction. I think they are condos or apartments; but from the water look like a professional building of windows topped with a strange middle-eastern looking cupula. Despite a low water level causing a very tight overhang, I tried the mini-Subterranean Slot from the west entrance. It was barely passable, and I managed to repeatably catch my paddle on the overhang. Gentle swell penetrated and I was concerned about getting the hull stuck in the basin drain while fooling around with my paddle so decided to back out and exit through the front of the passage – another interesting slot. Later, on the return from Off Rock, I was able to pass through from the east entrance. Galloupes rock faces and headland rock slots from the mini-Subterranean Slots to Off Rock continued to provide excellent runs in gentle swell. It was almost impossible not to exploit the swell energy if you paddled close in. The South Off Rock Slot in Figure 12 was completely underwater at a tidal depth estimated to be about five feet over MLLW. At low water the slot has a wonderful concentration of energy into the Off Rock Gut, but can also drive a kayak against the rock face. Today I was paddling my green Explorer that had been severely damaged in this slot about five years ago. I made a mental note to return to the South Off Rock Slot earlier in the tide cycle to record its height above water and thereby reference it to MLLW. The wider North Off Rock Passage was open for business at five feet over MLLW. I was able to get a nice push into the Off Gut. The return to the Puritan road put-in was a delight. Virtually windless up to Lincoln House Point and very calm. I saw large freighters heading for President Roads into Boston. One of them appeared to be moving quite fast, and I thought I could see a bow wave. I wondered if that wave could hit Galloupes; but if so, it was either very diminished or nonexistent. I was cheerfully greeted by a bicyclist on the rock face edge across from Dread. I pointed out that it may be difficult proceed further to the ledge islands, but the rider noted the bulbous tires on the bike. Hmm, another mode of coasteering! A practice roll at Lincoln House Point and a quick take-out at Puritan Road completed a perfect winter-time paddle. Total distance of about 10.7 nautical miles. Figure 9: Galloupes Pool Slot. (LAT 42o27.721’, LON -70o53.545’, high water). Figure 10: Galloupes Inner (LAT 42o27.806’, LON -70o53.415’, 4ft over MLLW) and Outer (LAT 42o27.783’, LON -70o53.408’) Pavilion Slots. Figure 11: Galloupes Mini-Subterranean Slots (LAT 42o27.841’, LON -70o53.371’, >4ft over MLLW). Figure 12: South (LAT 42o27.879’, LON -70o53.138’, mid to low water) and North (LAT 42o27.932’, LON -70o53.105’, 4ft over MLLW) Off Rock Passages. *Rule of Twelfths: Over a six hour tide cycle, hourly changes in depth are 1:2:3:3:2:1 x tidal range/12. Postscript: Straitsmouth Island on 12_30­_2021: During another trip a few days later on 12_30_2021 I was able to visit the extraordinary Straitsmouth Table a half hour after low tide. The Straitsmouth Table juts out east of the island and in conditions creates tremendous curling and surging waves. The adjacent Straitsmouth Passage and south facing coast have nearly perfect gardening and rock/ledge runs. The top circle in the left-side of Figure 13 shows the area of the Table. The Tidelog of 12_30 had a tidal range of 11ft. By the Rule of Twelfths, the water had risen 0.5*11/12 = .46ft. Conditions were rougher than 12_27, but I estimated that the Table was 3-4 feet higher than the water. Consequently, at LT it was probably 4 feet. The springs baseline with a quarter moon was at -0.4ft, below MLLW, so the estimate is a Straitsmouth Table about 3.5 feet above MLLW. The lower circle on the left side of Figure 13 and on the right-side image show a continuation of the Straitsmouth Table into the very challenging Straitsmouth Passage. When I ran the passage from the north end today, the rocks to the right were just barely awash. From the analysis above, that suggests a level at MLLW. Figure 13: Straitsmouth East Table and Passage (42o39.797’, -70o35.185’, Table at 3.5ft above MLLW, Passage at MLLW).